circadian biorhythms of the parameters of the excretory function of the kidneys. The chronorhythms of the functional state of the kidneys were studied round -the clock in every 2 hours after introducing mildronate (50mg/kg) at different times of the 24-hour period (8 00 , 12 00 , 16 00 , 20 00 , 24 00 , 04 00 ). The investigations were performed under the natural conditions of lighting against a background of water diuresis. The introductions of mildronate did not influence essentially on the

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... sor of the circadian biorhythm of the rate of the glomerular filtration (GF) and diuresis, however, the amplitude of the biorhythm increased by 30-40% respectively. In the daytime (12 00 -18 00 ) urine passage exceeded nocturnal diuresis by 30% with the GF rate at 12 00 . With the sinusoidal character of the chronogram of the concentration Na + ions and its excretion their indices significantly exceeded the control and maximum values during the period from 08 00 till 14 00 , irrespective of the time of introducing the agent. The mesor of Na + -uresis increased 1,6 times (Р < 0,05) with the acrophase of the biorhythm at 12 00 -14 00 (the excretion of Na + increased 1,6 times: during the bathyphase -04 00 -06 00 The mesor of K + -uresis increased 1,2 times. A biorhythm inversion is observed: during the bathyphase period in the control animals (16 00 , 24 00 ). K + -uresis reached a maximum value (it increased 2 times) upon injecting mildronate. The protein excretion was higher in the day-time of the 24 -hour period. Thus, an elevation of the indies of the excretory function of the kidneys is observed upon introducing mildronate in the first half of the day with the acrophase of Na + -uresis at 12 00 -14 00 hours, the latter may be taken into account upon obtaining a desired soluretic effect of the drug.